Separate AdblockChromium files and SDK libraries files

[asmirnov]

Background

We've added build config files (BUILD.gn) and some other files (python hooks) in third_party/libadblockplus, third_party/libadblockplus_common and third_party/libadblockplus_android. However we also clone libs sources to the same directories directly. So we're mixing files from AdblockPlusChromium repository and from github libraries repositories. It makes git status show files from AdblockPlusChromium repository showing as untracked files.

The good practise is to checkout libraries files to src subdirectories and exclude them from git tracking (.gitignore) in AdblockPlusChromium repository. It will simplify gclient sync too.

What to change

Checkout paths and build configs to use src for libraries files checked out from Github.

Tips for testers

Since it does not relate to any feature it's hard to test it (i'd say you can't test if you are not developer).
If Chromium can be compiled and launched it means it did not break it at least.

[asmirnov]

Duplicates #6535

[asmirnov]

Since now they libadblockplus and libadblockplus-android are now extracted to src subdirectories i'd suggest to clean third_party/libadblockplus and third_party/libadblockplus_android, check out them again and then gclient sync.