NEXUS-6099: Remove attribute upgraders

Conflicts:
	components/nexus-core/src/main/java/org/sonatype/nexus/proxy/attributes/DefaultAttributesHandler.java
	components/nexus-core/src/main/java/org/sonatype/nexus/proxy/attributes/upgrade/AttributesUpgradeEventInspector.java
	components/nexus-core/src/test/java/org/sonatype/nexus/proxy/attributes/Nexus4628Test.java
NEXUS-6099: Attr upgrade leftover
NEXUS-6099: Configuration trimmed to 2.0+
NEXUS-6099: Removed ancient config tests

Upgrade tests removed, as most of them made no sense
anymore, coz:
* they tested cases happened in 1.x line (moving out security, moving in
tasks)
* they tested some corner cases of customers happened in alphas
* upgrade is supported from 2.x from now on

We might add some new set of tests doing 2.0 upgrades
Merge remote-tracking branch 'origin/master' into NEXUS-6099-desupport-nx-1x

Conflicts:
	components/nexus-core/src/main/java/org/sonatype/nexus/configuration/application/upgrade/DefaultApplicationConfigurationUpgrader.java
	components/nexus-core/src/main/java/org/sonatype/nexus/configuration/application/upgrade/Upgrade103to104.java
	components/nexus-core/src/main/java/org/sonatype/nexus/configuration/application/upgrade/Upgrade104to105.java
	components/nexus-core/src/main/java/org/sonatype/nexus/configuration/application/upgrade/Upgrade105to106.java
	components/nexus-core/src/main/java/org/sonatype/nexus/configuration/application/upgrade/Upgrade106to107.java
	components/nexus-core/src/main/java/org/sonatype/nexus/configuration/application/upgrade/Upgrade107to108.java
	components/nexus-core/src/main/java/org/sonatype/nexus/configuration/application/upgrade/Upgrade108to140.java
	components/nexus-core/src/main/java/org/sonatype/nexus/configuration/application/upgrade/Upgrade1100to200.java
	components/nexus-core/src/main/java/org/sonatype/nexus/configuration/application/upgrade/Upgrade140to141.java
	components/nexus-core/src/main/java/org/sonatype/nexus/configuration/application/upgrade/Upgrade141to142.java
	components/nexus-core/src/main/java/org/sonatype/nexus/configuration/application/upgrade/Upgrade142to143.java
	components/nexus-core/src/main/java/org/sonatype/nexus/configuration/application/upgrade/Upgrade143to144.java
	components/nexus-core/src/main/java/org/sonatype/nexus/configuration/application/upgrade/Upgrade144to145.java
	components/nexus-core/src/main/java/org/sonatype/nexus/configuration/application/upgrade/Upgrade145to146.java
	components/nexus-core/src/main/java/org/sonatype/nexus/configuration/application/upgrade/Upgrade146to1100.java
	components/nexus-core/src/main/java/org/sonatype/nexus/configuration/application/upgrade/Upgrade200to220.java
	components/nexus-core/src/main/java/org/sonatype/nexus/configuration/application/upgrade/Upgrade220to250.java
	components/nexus-core/src/main/java/org/sonatype/nexus/configuration/application/upgrade/Upgrade250to270.java
	components/nexus-core/src/main/java/org/sonatype/nexus/proxy/attributes/DefaultAttributesHandler.java
	components/nexus-core/src/main/java/org/sonatype/nexus/proxy/attributes/DefaultFSAttributeStorage.java
	components/nexus-core/src/main/java/org/sonatype/nexus/proxy/attributes/LegacyFSAttributeStorage.java
	components/nexus-core/src/main/java/org/sonatype/nexus/proxy/attributes/upgrade/DefaultAttributeUpgrader.java
Merge remote-tracking branch 'origin/master' into NEXUS-6099-desupport-nx-1x

Conflicts:
	components/nexus-core/src/main/java/org/sonatype/nexus/configuration/application/upgrade/Upgrade103to104.java
	components/nexus-core/src/main/java/org/sonatype/nexus/proxy/attributes/DefaultFSAttributeStorage.java
	components/nexus-core/src/main/java/org/sonatype/nexus/proxy/attributes/LegacyFSAttributeStorage.java
	components/nexus-core/src/test/java/org/sonatype/nexus/configuration/application/source/FileConfigurationSourceTest.java
	components/nexus-core/src/test/java/org/sonatype/nexus/configuration/application/upgrade/DefaultApplicationConfigurationUpgraderTest.java
	components/nexus-core/src/test/java/org/sonatype/nexus/proxy/attributes/DefaultAttributeStorageIT.java
	components/nexus-core/src/test/java/org/sonatype/nexus/proxy/attributes/LegacyFSAttributeStorageTest.java
	components/nexus-core/src/test/java/org/sonatype/nexus/security/upgrade/SecurityConfigurationUpgradeTest.java
Merge remote-tracking branch 'origin/master' into NEXUS-6099-desupport-nx-1x

Conflicts:
	components/nexus-core/src/main/java/org/sonatype/nexus/configuration/application/upgrade/Upgrade103to104.java
	components/nexus-core/src/main/java/org/sonatype/nexus/proxy/attributes/DefaultAttributesHandler.java
	components/nexus-core/src/test/java/org/sonatype/nexus/configuration/application/source/FileConfigurationSourceTest.java
	components/nexus-core/src/test/java/org/sonatype/nexus/configuration/application/upgrade/DefaultApplicationConfigurationUpgraderTest.java
	components/nexus-core/src/test/java/org/sonatype/nexus/proxy/attributes/Nexus4628Test.java
	components/nexus-core/src/test/java/org/sonatype/nexus/security/upgrade/SecurityConfigurationUpgradeTest.java
Merge remote-tracking branch 'origin/NEXUS-6099-desupport-nx-1x' into NEXUS-6099-desupport-nx-1x
NEXUS-6099: Upgraded legacy ITs configurations
NEXUS-6099: Upgrade of default config
NEXUS-6099: Fixed license
NEXUS-6099: removed Nexus652Beta5To10UpgradeIT

IT that was testing an upgrade from Nx beta5 to 1.0!!!
NEXUS-6099: Lowring config version for Nexus4635FullUpgradeIT

To trigger "upgrade" (even if there is no change, only model version
changed).
NEXUS-6099: Nexus1563ExternalRealmsLoginIT configuration tweak

In old Nx config, the security information was embedded into
nexus.xml, later was pulled out into separate file. Not much
ITs depended on that, but this one was. Simply put, the information
that Simple Realm is needed for this IT was lost during "bare"
upgrade of nexus.xml from ancient version, as security was not
upgraded in this case (is happening in full Nx instance via
eventing).
Merge pull request #252 from sonatype/NEXUS-6099-desupport-nx-1x

NEXUS-6099: Desupport upgrades from Nx 1.x