Add .nb-gradle directory to .hgignore

.nb-gradle directory is created when browsing OpenJFX repository with Netbeans (installed with Gradle plugin [1]). This directory contains private caches of the projects and running the command 'hg st' will give output like:

? .nb-gradle\private\cache\apps-72210a8f723c1a5c9f8a01cd037f9c60
? .nb-gradle\private\cache\base-37a39452bc945f05cb67e225227dfae0
? .nb-gradle\private\cache\controls-4f9f6ecc97f424c3aa227121dba517fc
? .nb-gradle\private\cache\extensions-ac0fbbfc59becd85835437696de2cbe2
? .nb-gradle\private\cache\fxml-10ba0778e9430d055c42f70af78459bd
? .nb-gradle\private\cache\fxpackager-a42b299963aa5cdf179f771bbd9915fd
? .nb-gradle\private\cache\graphics-635dc1bebc8cb18180cbaf7ae5dfbb9d
? .nb-gradle\private\cache\jmx-08f8719436131f3933e6131ff9e5a1a6
? .nb-gradle\private\cache\media-b1a24309d0f973ce6f108ca97e7dfc70
? .nb-gradle\private\cache\rt-d41d8cd98f00b204e9800998ecf8427e
? .nb-gradle\private\cache\swing-52429da199196ab72657dbc5a04a5679
? .nb-gradle\private\cache\swt-5e2bcb57fd109126fa605362850571ab
? .nb-gradle\private\cache\system-68ff40186b1675474a727e7d6f83faf5
? .nb-gradle\private\cache\web-47b0e4eb1c8506fdf6cfea22f3578918
? .nb-gradle\profiles\private\aux-config

This directory shouldn't be part of version control and hence should be marked in .hgignore file.

[1] http://plugins.netbeans.org/plugin/44510/gradle-support


Proposed patch:

diff --git a/.hgignore b/.hgignore
--- a/.hgignore
+++ b/.hgignore
@@ -12,6 +12,7 @@
 ^.idea/inspectionProfiles/*
 ^.idea/copyright/profile_settings.xml$
 ^\.gradle/
+^\.nb-gradle/
 ^buildSrc/\.gradle/
 ^.idea/out/
 ^build/