title: J2SSH Core library - Unable find other custom key exchange algorithms implementation
body: <p>I am searching the implementation of key exchange algorithms for <code>j2ssh core 0.2.9</code> as below.</p>
  
  <pre><code>diffie-hellman-group-exchange-sha1
  diffie-hellman-group14-sha1
  diffie-hellman-group1-sha1
  ecdh-sha2-nistp256
  ecdh-sha2-nistp384
  ecdh-sha2-nistp521
  </code></pre>
  
  <p>Above all should be able to supports j2ssh core library version 0.2.9 and able to add them like how the existing j2ssh core library using key algorithm i.e DhGroup1Sha1 by default</p>
  
  <p>Currently, In my application, I am using <code>j2ssh</code> core library version[0.2.9]. Switching to other j2ssh library is not feasible for me due to some time constraints.</p>
  
  <p>Please help me out if you have any good solution </p>