more nesting in navs.less. code.less: cleanup styles that get immediately overriden later in the file. more nesting in buttons.less. use nesting more in pagination.less. more nesting in navbar.less.

BS3 commits 65141338df7e40151a813d33a1194ddcbf464046,
1045226544c6f9396227974b5543df1caf74f8cf,
b13417525c50c27d3fca64d6e0e3d2d7de91bedb,
e0d1b83e259395b25ba2b996372f68eede16f5e3,
46378c7ba3211134881f031a2fc8707e96706aad
code.less: cleanup styles that get immediately overriden later in the file. more nesting in buttons.less. use nesting more in pagination.less. more nesting in navbar.less

BS commits 1045226544c6f9396227974b5543df1caf74f8cf,
b13417525c50c27d3fca64d6e0e3d2d7de91bedb,
e0d1b83e259395b25ba2b996372f68eede16f5e3,
46378c7ba3211134881f031a2fc8707e96706aad