Fix automatic language detection for registered users

If you do not choose a language, the db pref record for your language is an empty string, but if you choose "automatic detection" and save your prefs, it's "auto".
"auto" in startup_gettext function prevents ttrss to choose the appropriate language.
Merge pull request #217 from ldidry/master

Fix automatic language detection for registered users
experimentally disable unnecessary folder icons for feedTree
Merge branch 'master' of github.com:gothfox/Tiny-Tiny-RSS
Revert "do not unlink lockfiles (closes #703)"

This reverts commit 9ffe8907dd8be17501601c5af53c73fd0f25ee04.
make_lockfile: check ino and dev fields for lock file (refs #703)
apply special feedTree styles only to main UI feedtree, fix feedParam and filterParam screwing with tree node layout
hide floatingTitle when first batch of headlines is received
add some inset shadow on container elements
update: do not explicitly fclose lockfile before unlinking (refs #703)