Focus: Replace Preconditions by Objects

Objects provides checks for nullness just like
Guava's Preconditions. Replacing by standard
java.util.Objects.

In addition some documentation updates.
Gitignore: Ignore some more Idea Configs
Idea Code Inspections

Added Idea Code Inspections to be used for
Selenium Extensions.
Introducing Idea Contract's

As proof-of-concept introducing IntelliJ Idea
Contracts.
More Tests for ValueParsers