Improve the Send Bitcoin page copy

[pavlenex]

@danielnordh suggested some things that can be improved in the Send Bitcoin page.

Whoever prefers can tackle it, as Daniel clearly explained what to change on that page.

See it here:

#181 (comment)

[johnsBeharry]

just a note on the comments about the Dos and Don'ts if we use the "Facts" component to show them it may resovle the problem of it sounding like a double negative.

[pavlenex]

#236