Added option to render_placeholder tag to set language

This is helpful in cases where the content of a placeholder in a specific
language should be displayed, independent of the user's language.
some documentation about the language argument for the render_placeholder tag
Merge pull request #1879 from piquadrat/feature/render-placeholder-language-2.4

Added option to render_placeholder tag to set language (2.4 branch)
Added tentative test for bug #1881
Fix test for 1881
Fixes exception when accesing reuqest.current_page within apphook view.
Merge pull request #1892 from czpython/apphook_patch_1

Fixes exception when accesing request.current_page within apphook view.
Fix copy-plugins operation

The previous edit to this file appears to have removed the declaration of the variable 'select'.  This edit sets that variable.

Signed-off-by: Martin Koistinen <mkoistinen@gmail.com>
Fix copy-plugins

Signed-off-by: Martin Koistinen <mkoistinen@gmail.com>
changelog
Merge pull request #1902 from mkoistinen/fix-copy-plugins

Fix copy plugins
Merge branch 'support/2.4.x' of github.com:divio/django-cms into support/2.4.x
locales
locales
missing locales
2.4.2 verison changed
authors, changelog
Fix tutorial with link to filer installation instructions
Merge pull request #1911 from yakky/feature/doc_filer_fix_24

Fix tutorial with link to filer installation instructions
Fixes #1004
Adding some information on using pip and virtualenv

Backport to 2.4 of #1908