Remote update frequency

[PaulWessel]

Description of proposed changes

Adds new defaults parameter GMT_DATA_SERVER_UPDATE [1d] to control frequency of catalog refresh on local computer. Also rearranges the description of global dataset with a leading chapter on how this is done, followed by sections per dataset. I also fixed a memory leak when a module called a module and the server catalog ended up being allocated twice.

I need help with arranging this correctly so that

1. The sidebar listing is sensible once we open Dataset
2. The size of headers is correct [===, ---, and ~~~ do not seem to work the way I thought]

[PaulWessel]

Wonder if GMT_DATA_SERVER_UPDATE is the best word. We want to convey interval, frequency, etc. I can go very long with

GMT_DATA_SERVER_UPDATE_INTERVAL

but it is a bit long. remove SERVER and go with GMT_DATA_UPDATE_INTERVAL?

[seisman]

Wonder if GMT_DATA_SERVER_UPDATE is the best word. We want to convey interval, frequency, etc. I can go very long with

GMT_DATA_SERVER_UPDATE_INTERVAL

but it is a bit long. remove SERVER and go with GMT_DATA_UPDATE_INTERVAL?

GMT_DATA_UPDATE_INTERVAL is good to me.

[PaulWessel]

looks pretty nice. If we are OK with merging this then I will wait for it to update on the web page and ask Sandwell and Müller if they would like any changes. Actually, before I do I think we should probably place their logos to give them more visual credit. I will do that later today - have another zoom then must drive all the way in to UH to pick up some books and a RAID system that needs work...

[seisman]

Looks good to me.

Also backport to 6.1 branch?

[PaulWessel]

I added the IGPP and EarthByte logos, at the end of each section, but looks bad. Need to move to the header for each section, and I think we could use a horizontal line between each data set section. Will head out now, if you have ideas to make this look good please do, else I will hack later.

[seisman]

I've added horizontal lines between each data sets.