angularjs: new package.

[Thomas:
  - improve the <pkg>_EXTRACT_CMDS so that the source files really end
    up directly under $(@D) and not in a subdirectory of it. It makes
    the rest of the package simpler and more standard.
  - remove capital letters in the package name in Config.in, and do
    other minor tweaks in Config.in]

Signed-off-by: Ignacy Gawędzki <ignacy.gawedzki@green-communications.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>