rename swap_*s methods to swap_*_indices and make the public

9 jobs from swap-indices-methods in 4 minutes and 7 seconds
Status Job ID Name Coverage
  Test
passed #40999
VS2013
VS2013-32-bit

00:00:56

passed #40998
VS2013
VS2013-64-bit

00:00:59

passed #40997
VS2015
VS2015-32-bit

00:01:23

passed #40996
VS2015
VS2015-64-bit

00:01:14

passed #40993
Linux
clang-c++11

00:02:21

passed #40995
Linux
cppcheck

00:00:29

passed #41000
Linux
doc

00:00:21

passed #40992
Linux
gcc-c++11

00:04:07

passed #40994
Apple
macos-c++11

00:02:49