bindings GYP: split off scripts

This factors out the pre-caching steps (lexer/parser tables and templates),
which are for internal use by the compiler and will need to be used
by both bindings_core and bindings_modules.
Also factors out the scripts/ and templates/ files to .gypi files,
so now well-factored.

R=haraken
TBR=Nico
BUG=358074

Review URL: https://codereview.chromium.org/302433005

git-svn-id: svn://svn.chromium.org/blink/trunk@174836 bbb929c8-8fbe-4397-9dbb-9b2b20218538