Update blockstack colors in bootstrap

[guylepage3]

Update all blockstack colors from blockstack brand v2 Issue stacks-archive/designs#65

• Grayscale colors for use across bootstrap
• Brand colors for use across bootstrap
• Deprecate old blockstack colors
• Apply new highlight color to bootstrap (see define new blockstack highlight color(s) designs#72)
• Apply button colors to bootstrap

[guylepage3]

New highlight colors have been chosen from the "blockstack label colors." See https://projects.invisionapp.com/boards/HE2VVROFSGB27/