Some improvments for wp-signup.php; wrong title for signup

[ocean90]

• use network_home_url()
• remove $current_site->path for subdomain install
• change privacy and email string, so that its the same as on install.php
• use get_home_url()
• Do not use "we"
• use network_admin_url()
• todo: the title shows a 404 message (Not found in 2010)

[ocean90]

with title fix

[wpmuguru]

@ocean90 - I think you put the patch on the wrong ticket.

[ocean90]

the real patch

[ocean90]

wpmuguru: Oops! I added the new one.

[wpmuguru]

(In [14575]) signup cleanup, props ocean90, fixes #13087