openstack/swift - swift - OpenDev: Free Software Needs Free Tools

This patch standardizes the CONTRIBUTING.rst file and adds the
required doc/source/contributor/contributing.rst
Swift already had a detailed CONTIRBUTING.rst and an informative
REVIEW_GUIDELINES.rst in the root of the repo. So we are also pulling
them into the contributor documentation so they can not only be easily
found in the checked repo but in the online documentation.
Change-Id: I4c84efbe50eb25ab922c9d6b69198dae341af48b

This is to fix the duplicated words issue, like:
 * "both of which which must be stripped off"
 * "In addition the the values set"
 and so on
Change-Id: Id3d84281f15815b4185c76874575e91a3589981b

Change-Id: I69f92aa9af160e4db2d5eb1e92545fc8ae050538

Change-Id: I9ed35d866ffb9faa41556c5c00f3b490d35412ab

Change-Id: I3acb3daeacb784c4038bf54d4103fab66c52f41a

Change-Id: I61304856a4ecccbbf3aa06c30822494592a3b3d5