Add option to 2500 demux

[karlnyr]

This PR adds:

• Option and default for lane number for HiSeq2500 flow cells

How to prepare for test:

• [x] ssh to hasta
• [x] install on stage: bash servers/resources/hasta.scilifelab.se/update-demux-stage.sh add/2500-demux-lane-option

How to test:

• [x] run bash /home/proj/stage/bin/git/demultiplexing/scripts/2500/demux-2500.bash with specified lane

Expected test outcome:

• [x] Script finishes
• [x] Passed lane is used
• [x] Take a screenshot and attach or copy/paste the output.

Review:

• [x] code approved by @Vince-janv
• [x] tests executed by @karlnyr
• [x] "Merge and deploy" approved by @karlnyr Thanks for filling in who performed the code review and the test!

This version is a:

• [ ] MAJOR - when you make incompatible API changes
• [ ] MINOR - when you add functionality in a backwards compatible manner
• [x] PATCH - when you make backwards compatible bug fixes or documentation/instructions

[karlnyr]

Test:

[karlnyr]

Deployed in prod: