Make BSD nicknames self-descriptive and conform to OSI site use

- don't require knowledge of 'new' or 'simplified' relative to *what*
- rm nickname for BSD 3-clause Clear License which is hidden and
  deserves to remain little known

_licenses/bsd-2-clause.txt

@@ -1,6 +1,6 @@
 ---
 title: BSD 2-clause "Simplified" License
-nickname: Simplified BSD
+nickname: BSD 2-Clause
 redirect_from: /licenses/bsd/
 family: BSD
 variant: true

_licenses/bsd-3-clause-clear.txt

@@ -1,7 +1,5 @@
 ---
 title: BSD 3-clause Clear License
-nickname: Clear BSD
-
 family: BSD
 variant: true
 

_licenses/bsd-3-clause.txt

@@ -1,6 +1,6 @@
 ---
 title: BSD 3-clause "New" or "Revised" License
-nickname: New BSD
+nickname: BSD 3-Clause 
 family: BSD
 variant: true
 source: http://opensource.org/licenses/BSD-3-Clause