Merge branch 'hotfix' into branch-2.0.2

# Conflicts:
#	angel-ps/mllib/src/test/java/com/tencent/angel/ml/logisticregression/LRTest.java

[DOCS] remove "online" and "offline" title as "FTRL" can be use onlin…

…e or offline

[DOCS] fix doc format

change spark version

[Release-1.5.1]

[Release-1.5.0] fix ut

[DOCS] change regression parameter name

Merge pull request Angel-ML#248 from liuzhanhao/patch-1

[DOCS] Fix typo

Merge branch 'branch-1.2.1' of https://github.com/Tencent/angel into …

…branch-1.2.1

Merge branch 'branch-1.2.0' of https://github.com/tencent/angel into …

…branch-1.2.0