issue #990: provide a more flexible way of finding translated content

This commit intorduces the TRANSLATIONS_PATTERN conf var
should be changed to a new default in v7
changed logic of locating original files and their translations

as it is hard to reverse-determine the original_name of a translated
post, rather remove translations from list of all files
rooted out other assumption about pattern file.ext.lang
flake: removed extra space after operator
docs: translated pages -> translated input pages

to reflect what we are talking about
update docs/manual.txt for TRANSLATIONS_PATTERN
the new recommended TRANSLATIONS_PATTERN will be path.lang.ext

+ a few modifications by Kwpolska
added tests for TRANSLATIONS_PATTERN
fixed tests for TRANSLATION_PATTERN
Merge pull request #992 from smartass101/translated_content_path

Translated content path: issue #990
fix the tests

Signed-off-by: Chris “Kwpolska” Warrick <kwpolska@gmail.com>
fix metadata detection for TRANSLATIONS_PATTERN

Signed-off-by: Chris “Kwpolska” Warrick <kwpolska@gmail.com>
actually fix the tests!

Signed-off-by: Chris “Kwpolska” Warrick <kwpolska@gmail.com>
Version 6.3.0

Signed-off-by: Chris “Kwpolska” Warrick <kwpolska@gmail.com>
add isso_helper.tmpl to theming.txt

Signed-off-by: Chris “Kwpolska” Warrick <kwpolska@gmail.com>
Move Arch instructions to the end, together with generic Linux distros paragraph.
Fix Windows section formatting.
Merge pull request #995 from ramiro/handbook-fixes

Misc. handbook fixes.
Update certain documents (add lead styling)

Signed-off-by: Chris “Kwpolska” Warrick <kwpolska@gmail.com>
make new_post error a bit more intelligent

Signed-off-by: Chris “Kwpolska” Warrick <kwpolska@gmail.com>