Start development of 1.5.2 as 1.6.0-RC3

Start development of 1.5.2 as 1.6.0-RC3

I might wait for some of the following PRs before merging this version mark.
- #2244 #2246 #2247 #2248 #2249

Changes during 1.5.1:

1.5.1 -> 1.5.2
	- Use gmodule instead of dlfcn for wider compatibility
	- Get/Set properties for tensor-filters & C-API.
	- Support C++ class as tensor-filter subplugin. (experimental. C++ filter API is not yet fixed)
	- Highly configurable Android build. (for smaller app binaries)
	- Tensor-Filter auto framework detection mode (C-API support)
	- Linux Foundation AI compliance & Github ORG migration
	- Upgraded Tensor-Filter API (C)
        - Applied portable logging mechanism.
        - Removed assertion failure for Tizen sensor errors.
	- OpenCV compatibility fixes.

	- Fixed issues found by static analyzers
	- More error/exception handling for robustness
	- Shows negative test case statistics

Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>