XCMS tools for plotting EIC and Peaks

[wverastegui]

This PR contains the XCMS plotting tools for peaks and EIC.

• Updated the help text
• Updated the test for mzML
• Renamed outputname, it inlcudes <m/z>, and <dataset_id>
• Fixed plot cutoff of the image
• Updated test plots

closes #498 & #499

[wverastegui]

This commit fixed the issue of the left margin cutoff.

[hechth]

Please see the comments and re-request review from me and @KristinaGomoryova after adressing them.

[hechth]

@yguitton should we put those tools rather to the other w4m XCMS tools into your repo, what do you think?
@jorainer these tools add some of the plotting capabilities described in your XCMS tutorial to Galaxy. If you make it referenceable we can link it here so that people see the further functions provided by the package :)

[yguitton]

@yguitton should we put those tools rather to the other w4m XCMS tools into your repo, what do you think?
@hechth Yes we should add that to W4M, as it really fits our users needs

[hechth]

@yguitton then I will close this here and open a new PR on w4m - should we make a new folder for these like xcms_plot or put them to the existing folder?