Provide a way to manage aliases for a major version of a tool #603
Description
As discussed in the sdkman/user-issues, it would be nice to have SDKMAN provide a way to manage additional aliases which would point to the latest major version of a tool.
This would be of great help when working with IDEs, since we would have a well defined aliases of, for example, major JDK releases: JDK 8, JDK 7, etc. So when a new update of a given JDK release would be installed, the alias would be updated to point to it and therefore no change to IDE configuration would be required.
I'm currently managing something like this by manually creating symlinks:
$ ll .sdkman/candidates/java/
total 28
drwxr-xr-x 7 vedran vedran 4096 Aug 31 07:59 ./
drwxr-xr-x 10 vedran vedran 4096 Jul 6 09:31 ../
drwxr-xr-x 9 vedran vedran 4096 Apr 18 17:40 6u93-zulu/
drwxr-xr-x 9 vedran vedran 4096 Apr 17 15:41 7u141-zulu/
drwxr-xr-x 8 vedran vedran 4096 Jul 12 13:41 8u141-oracle/
drwxr-xr-x 9 vedran vedran 4096 Jul 26 16:26 8u144-zulu/
drwxr-xr-x 10 vedran vedran 4096 Aug 21 16:59 9ea14-zulu/
lrwxrwxrwx 1 vedran vedran 47 Aug 9 09:09 current -> /home/vedran/.sdkman/candidates/java/8u144-zulu/
lrwxrwxrwx 1 vedran vedran 9 Aug 22 14:04 java-6-zulu -> 6u93-zulu/
lrwxrwxrwx 1 vedran vedran 10 Aug 22 14:04 java-7-zulu -> 7u141-zulu/
lrwxrwxrwx 1 vedran vedran 12 Aug 31 07:59 java-8-oracle -> 8u141-oracle/
lrwxrwxrwx 1 vedran vedran 10 Aug 22 14:04 java-8-zulu -> 8u144-zulu/
lrwxrwxrwx 1 vedran vedran 10 Aug 27 20:13 java-9-zulu -> 9ea14-zulu/Which results in:
$ sdk ls java
================================================================================
Available Java Versions
================================================================================
+ java-9-zulu
+ java-8-zulu
+ java-8-oracle
+ java-7-zulu
+ java-6-zulu
* 9ea14-zulu
9ea13-zulu
> * 8u144-zulu
* 8u141-oracle
8u131-zulu
* 7u141-zulu
* 6u93-zulu
================================================================================
+ - local version
* - installed
> - currently in use
================================================================================/cc @joshuawhite929