Enhancement of http destination

[ThisIsBenny]

• handle status codes 200, 201 and 202 as success
• remove upload files only on success
• use result.close() to avoid memory issues

[tbbuck]

I've tested this on my Enviro Urban and can confirm the result.close() fixes the issue where (for me) only 3 readings could be sent at a time before memory issues prevented the rest going through.

[Gadgetoid]

If I'm being pedantic I'd say the if statement should be reversed so that not in becomes in. Otherwise this looks good, thank you! Just waiting on @lowfatcode to have a moment spare from EPIC FONT STUFF to review this.

[lowfatcode]

Thanks all! I had been messing with the HTTP endpoint already so have manually added these fixes: cafed06