Enable extensions in separate header.
utils: str_replace
config: handle when merged config is empty
data: support %APP% path prefix.
config: use %APP% instead of /application
logging: support for increasing verbosity for std{err,out}.

Fixes #46.
Fixes warning in loading.cpp
Merge pull request #44 from ext/extensions

Enable extensions in separate header.
Merge pull request #47 from ext/misc_20131214

Misc 20131214
Merge branch 'master' into awesomnium