Add cucim.kit.cumed plugin with skeleton (rapidsai#129)

This change adds a skeleton plugin named `cucim.kit.cumed` for medical-related file loaders and image operations (e.g., .mhd file format support).

The image loader to use is determined by `is_valid()` method implemented in each plugin and CuImage object holds the reference to the image format descriptor (`cucim::io::format::ImageFormatDesc*`).

cuCIM treats `cucim.kit.cuslide` and `cucim.kit.cumed` plugins as built-in plugins, and it would support custom plugins in the future (by refactoring the framework code, according to the recent update of Carbonite (minimal) SDK library and use the library as it is).

Authors:
  - Gigon Bae (https://github.com/gigony)

Approvers:
  - AJ Schmidt (https://github.com/ajschmidt8)
  - Benjamin Zaitlen (https://github.com/quasiben)
  - https://github.com/jakirkham

URL: rapidsai#129

Author: gigony

CONTRIBUTING.md

@@ -144,11 +144,13 @@ The build command will create the following files:
 - `./install/lib/libcucim*`
 - `./python/install/lib/_cucim.cpython-*-x86_64-linux-gnu.so`
 - `./cpp/plugins/cucim.kit.cuslide/install/lib/cucim.kit.cuslide@*.so`
+- `./cpp/plugins/cucim.kit.cumed/install/lib/cucim.kit.cumed@*.so`
 
 And, it will copy the built library files to `python/cucim/src/cucim/clara/` folder:
 - `libcucim.so.*`
 - `_cucim.cpython-*-x86_64-linux-gnu.so`
 - `cucim.kit.cuslide@*.so`
+- `cucim.kit.cumed@*.so`
 
 
 **Building `cucim`(python bindings)**
@@ -173,14 +175,14 @@ Once it is built, the subsequent build doesn't take much time.
 
 However, if a build option or dependent packages are updated, the build can be failed (due to CMakeCache.txt or existing build files). In that case, you can remove use the following commands to remove CMakeCache.txt or build folder, then build it again.
 
-1) Remove CMakeCache.txt for libcucim, cuslide plugin, and the python wrapper (pybind11).
+1) Remove CMakeCache.txt for libcucim, cuslide/cumed plugin, and the python wrapper (pybind11).
 
 ```bash
 # this command wouldn't remove already downloaded dependency so faster than `clean` subcommand
 ./run build_local clean_cache
 ```
 
-2) Remove `build-*` and `install` folder for libcucim, cuslide plugin, and the python wrapper (pybind11).
+2) Remove `build-*` and `install` folder for libcucim, cuslide/cumed plugin, and the python wrapper (pybind11).
 
 ```bash
 # this command is for clean build

ci/release/update-version.sh

@@ -37,6 +37,7 @@ sed_runner 's/release = .*/release = '"'${NEXT_FULL_TAG}'"'/g' docs/source/conf.
 sed_runner "s/${CURRENT_LONG_TAG}/${NEXT_FULL_TAG}/g" VERSION
 sed_runner "s/${CURRENT_LONG_TAG}/${NEXT_FULL_TAG}/g" python/cucim/VERSION
 sed_runner "s/${CURRENT_LONG_TAG}/${NEXT_FULL_TAG}/g" cpp/plugins/cucim.kit.cuslide/VERSION
+sed_runner "s/${CURRENT_LONG_TAG}/${NEXT_FULL_TAG}/g" cpp/plugins/cucim.kit.cumed/VERSION
 sed_runner "s#\[Version ${CURRENT_LONG_TAG}\](release_notes/v${CURRENT_LONG_TAG}.md)#\[Version ${NEXT_FULL_TAG}\](release_notes/v${NEXT_FULL_TAG}.md)#g" python/cucim/docs/index.md
 sed_runner "s/v${CURRENT_LONG_TAG}/v${NEXT_FULL_TAG}/g" python/cucim/docs/getting_started/index.md
 sed_runner "s#cucim.kit.cuslide@${CURRENT_LONG_TAG}.so#cucim.kit.cuslide@${NEXT_FULL_TAG}.so#g" python/cucim/docs/getting_started/index.md