NEXUS-7575: UA not set for some HTTP exchanges

Like HTTP CONNECT for tunneled proxy. Applied fix
and added UT that checks some cases and verifies UA
is set.
Brings "Reset User Tokens" form in-line with 8shapes mockups

+ Breaks dialog out of its frame
+ Left-aligns the title, body, and footer
+ Removes background color from all save/discard toolbars across the app
+ Left-aligns the save button with associated content across the app
Restores hover state to mode buttons
Fixes line height of detail header so descenders aren't obscured
Merges in changes from master
Adds margin, renames ui style, and adds no-border option
Adjusts line height of subsection header to avoid cropped descenders
Removes extra padding from the top of settings forms
Merge pull request #817 from sonatype/8shapes_nested

Brings "Reset User Tokens" form in-line with 8shapes mockups
Creates a global index of colors
Add support to control what flavors are built with -Dflavors
tidy
simplify flavor execution
[NEXUS-7596] Only activate Yum capabilities if create/mergerepo are available

commit 0e487008eb2ae646c53d5e5bcc01a48580535252
Merge: af44205 c382117
Author: Alin Dreghiciu <adreghiciu@gmail.com>
Date:   Fri Oct 24 10:23:22 2014 +0300

    Merge remote-tracking branch 'origin/nexus-2.11.x' into nexus-2.11.x-NEXUS-7596-check-createrepo

    Conflicts:
    	plugins/yum/nexus-yum-repository-plugin/src/main/java/org/sonatype/nexus/yum/internal/task/MergeMetadataTask.java

commit af44205ca6ed36f70eed7372d652ddcb6ee4623f
Author: Alin Dreghiciu <adreghiciu@gmail.com>
Date:   Thu Oct 23 22:12:55 2014 +0300

    [NEXUS-7596] Add @Nullable / JavaDoc

commit e23251b6a7edec38d755c6f702e93c4dfeee37d3
Author: Alin Dreghiciu <adreghiciu@gmail.com>
Date:   Tue Oct 21 23:20:13 2014 +0300

    [NEXUS-7596] Tidy

commit 7621c9e753048e94d2e4590177bdd6408e8deb95
Author: Alin Dreghiciu <adreghiciu@gmail.com>
Date:   Tue Oct 21 23:17:42 2014 +0300

    [NEXUS-7596] Remove wrong activation condition

commit f7bd8c6e64113acecfcf6bc82f3628b40fc15163
Merge: 2e4b74c aeee5a0
Author: Alin Dreghiciu <adreghiciu@gmail.com>
Date:   Tue Oct 21 23:12:31 2014 +0300

    Merge remote-tracking branch 'origin/nexus-2.11.x' into nexus-2.11.x-NEXUS-7596-check-createrepo

    Conflicts:
    	plugins/yum/nexus-yum-repository-plugin/src/main/java/org/sonatype/nexus/yum/internal/task/GenerateMetadataTask.java

commit 2e4b74c3f773d7edd8a6bbd20ab291815754e4a6
Author: Alin Dreghiciu <adreghiciu@gmail.com>
Date:   Tue Oct 21 23:07:32 2014 +0300

    [NEXUS-7596] Tidy

commit 906a2250fb4c6daa2eef70433e0f410941f1a871
Author: Alin Dreghiciu <adreghiciu@gmail.com>
Date:   Tue Oct 21 23:06:40 2014 +0300

    [NEXUS-7596] Validate detected create/mergerepo version

commit 1bb30816e64f658e72994a46cd9856eccd2c47ea
Author: Alin Dreghiciu <adreghiciu@gmail.com>
Date:   Tue Oct 21 21:19:04 2014 +0300

    [NEXUS-7596] Add optional paths to create/mergerepo

commit 3d301f3613f6e339c72d82cef48a7b3b94593ee3
Author: Alin Dreghiciu <adreghiciu@gmail.com>
Date:   Mon Oct 20 15:52:16 2014 +0300

    [NEXUS-7596] Only activate Yum capabilities if create/mergerepo are available

Conflicts:
	plugins/yum/nexus-yum-repository-plugin/src/main/java/org/sonatype/nexus/yum/internal/capabilities/YumCapabilityDescriptor.java
	plugins/yum/nexus-yum-repository-plugin/src/test/java/org/sonatype/nexus/yum/internal/task/MergeMetadataTaskTest.java
NEXUS-7521: simple Asset hashing service based on Guava's thread-safe hashing functions
NEXUS-7521: introduce AssetHasher API, support both direct use of AssetHashers values and injection of them as @Named implementations of AssetHasher
Alters the shape and color of buttons in the header

+ Makes the mode buttons invert on hover/focus
+ Changes the alert, refresh, logout, and help icons to a square format
Brings colors more in-line with the 8shapes visual index
Ties text body size and colors to 8shapes visual index
Changes background color of developer bar to smalt