disclaimer adjustments

[stufraser1]

User centred design expert has advised disclaimer is too long and obscure message of tool. To improve.

[stufraser1]

ref #848 - additional feedback this should be changed

[fjacon]

@stufraser1 should we do something asap about #848 ?

[stufraser1]

Would be happy to have this resolved soon.
Can you quickly make it appear only on first use?
What other implications for related work: if we are to record a users' first and subsequent use of the site, will that require holding cookies, etc? What implications of this for GDPR - do we have to add another annoying pop-up to warn people we store cookies, etc?
I expect that if this is only shown once, we can keep the text as it is; About page can be amended to accomodate any additional info for users to check on subsequent uses.