Support prerelease and metadata info for next command #247

When creating prereleases we should be able to use changie next to find the next version while including prerelease data.
This should also allow for metadata.

Next should start from the latest standard release without prerelease info, metadata should be ignored.

Example:
v1.2.0-b1
v1.1.9
next major = v2.0.0
next minor = v1.2.0
next patch = v1.1.10

Prerelease and metadata allows for many values to be included and are dot separated.

Example:
v1.4.2
next major --pre rc1 = v2.0.0-rc1
next minor --pre b1 --pre debug = v1.5.0-rc1.debug
next patch --meta ab31ab54 = v1.4.3+ab31ab54
next minor --pre b1 --meta cursed = v1.5.0-b1+cursed

Part of #237