title: Change UITableView section header/footer WHILE RUNNING the app?
body: <p>I'm facing a problem I cannot resolve...
  I have a grouped table whose section header and section footer get displayed correctly upon launch thanks to</p>
  
  <pre><code>- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section
  </code></pre>
  
  <p>and</p>
  
  <pre><code>- (NSString *)tableView:(UITableView *)tableView titleForFooterInSection:(NSInteger)section
  </code></pre>
  
  <p>Yet, I can't figure out how to update them later, I don't know how to change those texts and it's quite frustrating because in my mind it had to be nothing harder than changing a text label or whatever... (some ".text" property...)</p>
  
  <p>I searched all through the documentation with no luck...</p>
  
  <p>Any help is highly &amp; kindly appreciated!
  Regards,
  Enrico</p>