Add support for maven repository

Description

Some of our projects uses maven as source of precompiled jar files. It could be a good idea to automatic search for the latest version of such dependencies.

Proposal

Add new source type (maven) to autoupdater. Use maven central api for this purpose.

Example

Rundeck core

For rundeck-core package we can request following url https://search.maven.org/solrsearch/select?q=g:%22org.rundeck%22a:rundeck-core&wt=json

in response it will return json:

{"responseHeader":{"status":0,"QTime":1,"params":{"q":"g:\"org.rundeck\"a:rundeck-core","core":"","spellcheck":"true","indent":"off","fl":"id,g,a,latestVersion,p,ec,repositoryId,text,timestamp,versionCount","start":"","sort":"score desc,timestamp desc,g asc,a asc","spellcheck.count":"5","rows":"","wt":"json","version":"2.2"}},"response":{"numFound":1,"start":0,"docs":[{"id":"org.rundeck:rundeck-core","g":"org.rundeck","a":"rundeck-core","latestVersion":"3.1.0-20190731","repositoryId":"central","p":"jar","timestamp":1564630302000,"versionCount":111,"text":["org.rundeck","rundeck-core","-sources.jar","-javadoc.jar","-tests.jar",".jar",".pom"],"ec":["-sources.jar","-javadoc.jar","-tests.jar",".jar",".pom"]}]},"spellcheck":{"suggestions":[]}}

so we can use response.docs[0].latestVersion to get latest stable version of package