Copy env's pybabel into base dir to fix string extraction

The jinja2 extracter needs to know about our custom HighlightExtension (used on
pages such as get-involved/develop/applications), which is not in the env's
python path. Copying pybabel into the base dir gives it access to our modules.
This is only required for string extraction; other scripts use pybabel from the
env directly.

If the env's pybabel version is updated, this copy must also be updated.

extract-messages.sh

 #!/bin/sh
 . ./translation.vars
 
-TZ=UTC env/bin/pybabel extract --msgid-bugs-address="http://trac.i2p2.de" \
+TZ=UTC ./pybabel extract --msgid-bugs-address="http://trac.i2p2.de" \
                                --project=$PROJECT \
                                --version=$VERSION \
                                -F $BABELCFG \

i2p2www/babel.cfg

 [python: **.py]
 [jinja2: **/pages/**.html]
+extensions=jinja2.ext.autoescape,jinja2.ext.with_,i2p2www.extensions.HighlightExtension
 [jinja2: **/blog/**.rst]
 extensions=jinja2.ext.autoescape,jinja2.ext.with_

pybabel

+#!env/bin/python
+# EASY-INSTALL-ENTRY-SCRIPT: 'Babel==0.9.6','console_scripts','pybabel'
+__requires__ = 'Babel==0.9.6'
+import sys
+from pkg_resources import load_entry_point
+
+if __name__ == '__main__':
+    sys.exit(
+        load_entry_point('Babel==0.9.6', 'console_scripts', 'pybabel')()
+    )