Use relative URLs and fix anchor links

BS3 commits: 72d4fafd6636b8b59c8c0983a2c27908a25d1a70
Replace @screen-sm with @screen-sm-min

BS3 commits: 055705741e97de3ffa98e9046facb5a92a7b4343
Group repo vars together in Jekyll config

BS3 commits: c7eac32d3e6e7993bd19f9005aa29df1f4eba8e6
Fix typos

BS3 commits: 711d0b833770264ab9a532267e84db1c9b951a13
Replace getElementsByTag with querySelector in IE10 Mobile viewport JS snippet

BS3 commits: 41257fe794f6c8dbb1a7bf3a33fea3187a1565e9
Use mix of medium and small grid clases on dashboard example

BS3 commits: 1d0bf580c99e9b03a4219c8aa4e313808bccbf10
document single .form-control per .input-group limitation; fixes 12109

BS3 commits: 6684005f63a851810548d3bcd7ca0460c953050e
harmonize footer links on homepage & docs pages

BS3 commits: 5fc434c5f1f86978670df2a3bdb0e3bd9fb6da81
better grouping of Bootstrap variables and fix Bootstrap links