Updated and improved Latvian translations

[arvislacis]

This PR updates Latvian translation files with some missing messages since the last time Latvian translation files were reviewed.

Also fixed some small typos and changed name of "components" to equally similar Latvian word which sounds better and is used more often in daily language.

[what-the-diff]

• Fixed typos in Latvian language files.
• Added missing translations for the backend and cms modules, as well as system module's locale section (for languages).
• Updated documentation links to point to new docs website: https://docs-lv.wintercms.com/ instead of old one: http://octobercms-latvia-documentation.readthedocs-hosted.com/.

[bennothommo]

Thanks @arvislacis!