add dub init deimos type
typo
add clean-caches command

- purges all dub metadata caches
- currently this is only the cache of the registry package supplier
Improve JSON parser error format. Fixes #317.

Errors are now displayed as "file(line): Error: message".
Remove obsolete field from BuildGenerator.
Add basic documentation for the Generator class and improve method protection.
Add "packageManager" property to Project.
Remove PackageManager argument from createProjectGenerator().

The argument is also removed from all Generator sub classes.
Add some more documentation in the Generator class.
Mention what to do with linkDependencies when building.
Fix build error on CI build.
Merge pull request #431 from MartinNowak/deimosInit

add dub init deimos type
Mention "deimos" for "dub init -h". See #431.
Merge pull request #432 from MartinNowak/typo

Fix typo.
Merge pull request #433 from MartinNowak/cleanCaches

Add clean-caches command for purging the metadata cache.
Use the actual binary name used to build DUB as the default compiler. See #303.
Attempt to test on compilers ranging from 2.064-2.066.
Second attempt.
Third attempt.
Fourth attempt.