1.5.0 Alpha

Kotlin compiler upgraded to 1.5.0

Fixes:

Make module name optional in CLI (#1850)
Fix line separator issues (#1887)
Fix preserving spaces in Javadoc comments (#1923)
GFM renderer: sanitize line ends (#1936)
Fix rendering html in briefs (#1931)
Fix code blocks on Extension Points page (#1948)
Remove extra dash (#1968)
Don't use older dir from previous runs in versioning (#1963)
Change jekyll links to be .html (#1990)
Fix Gradle plugin application (#2000)

Added features:

Add a supertype for leaf dokka tasks that defines dokkaSourceSets (#1891)
Add ability to specify older versions as a list of files (#1890)
Cachable Gradle task (#1905)
Multilanguage docs inheritance (#1951)
Logging levels in CLI (#1976)
Flatten multi-module structure (#1980)

Special thanks to external contributors: @rnett, @msink, @zsmb13, @rachelcarmena and @hfhbd