0.7.0 release

• Partial rewrite for library to use asyncFx threads for JavaFx related work so that works ok also when testing with multithreaded applications. As JavaFX UI is not thread safe earlier implementation could lead to dead lock.
• Improved keyword failure printouts
• Documentation update:
  o removed usage of old locator syntax (fixes #13)
  o general improvements for new library users
• Empty locators are not allowed anymore (fixes #46)
• Timeout improvements:
  o there is general library timeout for keywords, for Wait Until* keywords there is keyword specific timeout (fixes #12)
  o Wait Until* keywords really waits for the timeout and does not exit before timeout
• Bump junit from 4.13 to 4.13.1 (low severity security vulnerability)