Messages refactoring and add progress information

[bertfrees]

Summary of the changes:

• Adapt to new messaging system (https://github.com/daisy/pipeline-framework/pull/127)

  • Use px:message and px:progress attributes
  • Make use of support for sending messages to execution log from Java
  • Added a pf:message step (and derived functions pf:error, pf:warn, pf:info, pf:debug and pf:trace) for logging from XSLT with other level than INFO
  • Added a pf:progress function to send progress info from XSLT

• Add new log messages and progress information, tweak existing messages and log levels

• Improved stack traces for exceptions inside custum steps (see also https://github.com/daisy/pipeline-framework/pull/127)

• Suppress XSLT warning messages (https://github.com/daisy/pipeline-mod-braille/issues/38)

• Examples of how to use Logback encoder for progress messages in tests (https://github.com/daisy/xproc-maven-plugin/pull/24)

• Rename "validation-status" port to "status"

  Also rename d:validation-status element

  see https://github.com/daisy/pipeline-mod-braille/issues/124#issuecomment-299941785

Depends on:

• https://github.com/daisy/pipeline-framework/pull/127
• https://github.com/daisy/pipeline-build-utils/pull/42
• https://github.com/daisy/xproc-maven-plugin/pull/24

Can be tested on https://github.com/daisy/pipeline/compare/messages.

[bertfrees]

Here also I don't understand why Travis doesn't work.

[bertfrees]

I've added a summary. I don't need an in-depth review of all the individual messages of course, but it would be nice if you could look at the changes related to https://github.com/daisy/pipeline-framework/pull/127 (the new messaging system and improved exception handling).

[bertfrees]

Merged in ff452f54c6244ead9c9941e97d5d16b0a110c4fc