[SPARK-10027] [ML] [PySpark] Add Python API missing methods for ml.feature

[yanboliang]

Missing method of ml.feature are listed here:
StringIndexer lacks of parameter handleInvalid.
StringIndexerModel lacks of method labels.
VectorIndexerModel lacks of methods numFeatures and categoryMaps.

[SparkQA]

Test build #41248 has finished for PR 8313 at commit 953ca82.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):
  • class StringIndexer(JavaEstimator, HasInputCol, HasOutputCol, HasHandleInvalid):
  • class HasHandleInvalid(Params):

[holdenk]

Exposing labels from StringIndexerModel is also in #7976 but its pretty much the same so should be fine.

[Lewuathe]

Some other classes has no shared accessor class (e.g. StandardScaler, RegexTokenizer) corresponding to arbitrary properties. It might be better to keep handleInvalid only inside of StringIndexer or create other shared accessor classes for StandardScaler etc to standardize the way of accessing to arbitrary properties.

[yanboliang]

handleInvalid is common property and other Transformer/Estimators may use it in future, so I think we need to make it shared param. Another reason is that we want to make Python consistency with Scala, and handleInvalid in Scala is shared param.
@jkbradley

[holdenk]

Maybe add a test for numFeatures & categoryMaps?

[yanboliang]

@holdenk Agree, done.

[SparkQA]

Test build #42183 has finished for PR 8313 at commit 86353b4.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):
  • class StringIndexer(JavaEstimator, HasInputCol, HasOutputCol, HasHandleInvalid):
  • class HasHandleInvalid(Params):

[SparkQA]

Test build #42199 has finished for PR 8313 at commit 4eb5607.

• This patch fails PySpark unit tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):
  • class StringIndexer(JavaEstimator, HasInputCol, HasOutputCol, HasHandleInvalid):
  • class HasHandleInvalid(Params):

[SparkQA]

Test build #42201 has finished for PR 8313 at commit 5403ae2.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):
  • class StringIndexer(JavaEstimator, HasInputCol, HasOutputCol, HasHandleInvalid):
  • class HasHandleInvalid(Params):