Fix detection and processing of .app.src.script

Loading .app, .app.src or .app.src.script returns now the value as per
the documentation (was wrapped in a list in some cases).

More places in the code detect .app.src.script and handle it.
add tests for processing .app.src{.script} files
Merge branch 'app_src_script' into erlide
handle configuration when rebar is not invoked as a script
make ?ERROR log normally, not directly to stderr
print out info about total number of files to be processed

this is useful to provide a progress report
eclipse project files