Overwrite host and webroot when forcessl is enabled

This patch enables the use of forcessl together with a multiple domains
reverse SSL proxy (owncloud/core#1099) which have different hostname
and webroot for http and https access. The code assumes that the ssl
proxy (https) hostname and webroot is configured via overwritehost and
overwritewebroot.
request.php: add type check to the not empty check of a string

The not equal comparison (<>) of a variable with an empty string
could lead to false positive results as the compare do not check
the type and thereby could not make sure that the checked variable
is a string. The usage of the not identical comparison operator
(!==) make sure that the variable is a string and not empty.
fixed xsendfile zip generation race condition
turn off autocompletion for password field

refs #2632
Fix OC_User::getDisplaynames when using numeric user id's

fixes #2948
merge translations with those from theme
merge translations with those from theme
additional safety checks
correct primary color to #1d2d44 where slightly wrong
make textarea inherit ownCloud font instead of using monospace
move warning and error states together in CSS, to be cleaned up
move password warning more relevant below password field, un-nest log in warning
remove unnecessary border from navigation, looked strange with scrollbar and pushed the text over 1px
Let autoloader resolve paths under apps lib directory.
Priorize common languages.
Don't use empty session.cookie_path, otherwise we get multiple cookies
Added explanation
Make divider not selectable

Very hacky
[tx-robot] updated from transifex
modify password clone to password type right on submit to prevent the browser remind the content