Feature Request 55 - Partial build (image generation)

[MickeJohannesson]

Solution that will only regenerate images for updated PUML files - #55
This will only act when doing local images generation

• It will generate a checksum of all PUML files during a run
• If the checksum is same for the PUML (and image exists) it will copy back image from a backup folder
• If the checksum is not the same it will regenerate the image
• To enhance performance the DIST folder is renamed to backup folder (instead of copy everything)
• All checksums will be saved in root of the project (_checksums.json). If unable to read it a full generation will take place.

Also moved some part out of the inner for loop, because it will never change during a run and no need to re-evaluate

For my current project it takes about 35s to generate a site with local images.
On update it takes about 2-4s depending on complexity of PUML diagram.

[adrianvlupu]

Excelent work. Thanks a lot for this. The only thing I changed is the need for the json file holding the array. I wrote it to the .c4builder file.