created i18n-service
added i18n filter an simple directive

translate strings/html in templates and partials now with filter or
directive:

* <div>{{"my text" | i18n}}</div>
* <div my-i18n>my text</div>
* <my-i18n>my text</my-i18n>
added i18n directive with formats and params for translation

insert html blocks now as parameters into i18n strings instead of
"translating" them
added i18n support for ngPluralize

transparently localize ngPluralize directives by translating then value
of the "when"-attribute before ngPluralize compiles it
integrated i18n config/locale selection in settings modal
Bugfix: reload angular-locale on locale change as well

ngLocale/$locale is used for formatting times and dates and should be
the same locale as our i18n implementation

still todo: find a better/more reliable way to load the
angular-locale.js
put current locale in consideration for various caches in filters/services

some local caches now need to be purged when the locale is changed on
runtime or else they'll still display strings in the wrong locale/language
added named params to my-i18n-format directive

named parameters allow for more readability
integrated i18n in all modules

every string in the modules to be displayed should now be passed through
"_" first
integrated i18n into all partials

as in the previous commit every string to be displayed in the partials
should now bei passed through "_" first
created (dummy) locale en-us as i18n template

extracted all strings out of the partials an modules so the en-us locale
should provide a complete template for localization
Bugfix: correctly interpolate placeholder of emoji-wysiwyg-editor with i18n
added german locales
Added documentation/guide for the new i18n module
Merge branch 'i18n'
use proper load event when loading new angular-locale
allow for html templates as params to i18n

allow params to be parsed as templates now so we exclude inlined html
from the message strings, e.g:

_('Welcome to {link: Telegram}', {link: '<a href="https://telegram.org/">{0}</a>'});
=> Welcome to <a href="https://telegram.org/">Telegram</a>

see discussion at https://github.com/zhukov/webogram/pull/452
start counting from 0 in i18n messages now

the previous commit changed this
removed html links from i18n messages