feat(server): support png and jpg type contrib icons

[ppaidi]

Description

We are supporting only SVG type of images as contribution icons, extending support to PNG and JPG image types.

Motivation and Context

Part of #1261

How has this been tested?

Mock trigger and activity with custom icons are available at fcastill/flogo-contrib-test. Added test PNG and JPG icons to the contributions, listed below

SVG type

Support for SVG type icon can be tested by installing below contributions

• github.com/fcastill/flogo-contrib-test/activity/log

• github.com/fcastill/flogo-contrib-test/trigger/timer

PNG type

Support for PNG type icon can be tested by installing below contributions

• github.com/fcastill/flogo-contrib-test/activity/error

• github.com/fcastill/flogo-contrib-test/trigger/channel

JPG type

Support for JPG type icon can be tested by installing below contribution

• github.com/fcastill/flogo-contrib-test/trigger/loadtester

Non image type

Show warning message describing the issue and mention supported types. This can be tested by installing below contribution

• github.com/fcastill/flogo-contrib-test/trigger/tcpudp

Unable to resolve icon

Can be tested by installing below contribution

• github.com/fcastill/flogo-contrib-test/activity/counter

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Refactoring (no functional changes, no api changes)
• [ ] Build/CI related changes
• [ ] Documentation related changes
• [ ] Other... Please describe:

Checklist:

• [x] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.