Update changelog and package.xml to 0.7.0

[j-rivero]

Following #532 and after checking with @scpeters and @SeanCurtis-TRI I think we are ready to run a new fcl version, 0.7.0.

I've included everything I found in v0.6.1...master in the Changelog.
Fixes #532

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This change is 

[sherm1]

Thanks @j-rivero!
+@sherm1 for a cursory review
with one minor comment

Reviewed 2 of 2 files at r1, all commit messages.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @j-rivero)

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CHANGELOG.md, line 3 at r1 (raw file):

## FCL 0

### FCL 0.7.0 (2021-08-xx)

nit: 2021-09-xx now

[j-rivero]

nit: 2021-09-xx now

Thanks @sherm1 ! I've set the release date to today.

[sherm1]

OK, I'll merge this now. What else do we need to do to complete the 0.7.0 release?

Reviewed 1 of 1 files at r2, all commit messages.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @j-rivero)

[j-rivero]

OK, I'll merge this now. What else do we need to do to complete the 0.7.0 release?

Thanks Michael. We need to run a new release in github. Going probably to https://github.com/flexible-collision-library/fcl/releases/new , Following previous release, we can use v0.7.0 as the tag, FCL 0.7.0 as tittle, and in the summary maybe just copy paste the Changelog.

[sherm1]

@scpeters is working on that. Current question is whether the version tag should be 0.7.0 or v0.7.0. Any opinion @j-rivero?

[j-rivero]

@scpeters is working on that. Current question is whether the version tag should be 0.7.0 or v0.7.0. Any opinion @j-rivero?

I think that it would be good to follow the previous schema. Said that, I looked into the releases and tags again and seems like only the 0.6.1 was done using the prefix v but there is also a 0.6.1 tag without prefix. With this, probably the best option is back to use 0.7.0 without v. Thanks @sherm1 , @scpeters

[sherm1]

OK, thanks @j-rivero -- I'll publish the release with tag 0.7.0 tomorrow unless anyone objects. We can always add a v0.7.0 tag to the same commit later if anyone cares.