[SPARK-1357] [MLLIB] Annotate developer and experimental APIs

Annotate developer and experimental APIs in MLlib.

Author: Xiangrui Meng <meng@databricks.com>

Closes #298 from mengxr/api and squashes the following commits:

13390e8 [Xiangrui Meng] Merge branch 'master' into api
dc4cbb3 [Xiangrui Meng] mark distribute matrices experimental
6b9f8e2 [Xiangrui Meng] add Experimental annotation
8773d0d [Xiangrui Meng] add DeveloperApi annotation
da31733 [Xiangrui Meng] update developer and experimental tags
555e0fe [Xiangrui Meng] Merge branch 'master' into api
ef1a717 [Xiangrui Meng] mark some constructors private add default parameters to JavaDoc
00ffbcc [Xiangrui Meng] update tree API annotation
0b674fa [Xiangrui Meng] mark decision tree APIs
86b9e34 [Xiangrui Meng] one pass over APIs of GLMs, NaiveBayes, and ALS
f21d862 [Xiangrui Meng] Merge branch 'master' into api
2b133d6 [Xiangrui Meng] intial annotation of developer and experimental apis