Switched off sorting in statement of assets view

Accidentally, some columns were sortable. However, since the statement
of assets view is grouped (summary lines, etc.), plain sorting does not
work.

Issue: #172
Added message if menu item is not applicable (Linux only)

Menus on Linux are not disabled (most likely due to a Ubuntu Unity bug).
Added a message box if the user picks such a menu item.

Issue: #178
Release 0.14.3
Next development version 0.14.4-SNAPSHOT
Fixed issue on OS X Yosemite not showing first line of tables

Issue: #181
Eclipse-Bug: https://bugs.eclipse.org/bugs/show_bug.cgi?id=446534
Fixed event registration that prevented the check for updates upon startup
Release 0.14.4
Ignored a BadPaddingException if the encrypted stream is not read completely

As reported on the forum, a BadPaddingException prevents opening an
encrypted ".portfolio" file. The issue occurs with one of the latest
Java updates. I was able to reproduce it with 1.8.0_25 while it is not
happening with 1.8.0_05.
Release 0.14.5
Next development version 0.14.6-SNAPSHOT
Added travis ci configuration
Added travis build commands to point to maven pom
Made travis test phase offline
Added build status image
Fixed more issues on OS X Yosemite not showing first line of tables

Issue: #181
Eclipse-Bug: https://bugs.eclipse.org/bugs/show_bug.cgi?id=446534
Fixed travis configuration to actually run tests
Merge branch 'master' into feature_currencies
Added currency columns to securities and accounts
Added exchange rate provider API
Added ECB exchange rate provider