Implement blackbox in Golang (#250)

* Initial release

integrationTest/test_data/000-admin-list.txt

@@ -0,0 +1,2 @@
+user1@example.com
+user2@example.com

integrationTest/test_data/000-file-list.txt

@@ -0,0 +1,2 @@
+bar.txt
+foo.txt

integrationTest/test_data/000-status.txt

@@ -0,0 +1,9 @@
++-------------+------------------------+
+|   STATUS    |          NAME          |
++-------------+------------------------+
+| BOTHMISSING | status-BOTHMISSING.txt |
+| DECRYPTED   | status-DECRYPTED.txt   |
+| ENCRYPTED   | status-ENCRYPTED.txt   |
+| GPGMISSING  | status-GPGMISSING.txt  |
+| SHREDDED    | status-SHREDDED.txt    |
++-------------+------------------------+

integrationTest/test_data/alice-cat-plain.txt

@@ -0,0 +1 @@
+I am the foo.txt file!

integrationTest/test_data/basic-status.txt

@@ -0,0 +1,5 @@
++-----------+---------+
+|  STATUS   |  NAME   |
++-----------+---------+
+| ENCRYPTED | foo.txt |
++-----------+---------+

integrationTest/test_data/reencrypt-plain.txt

@@ -0,0 +1 @@
+I am the foo.txt file!

integrationTest/test_data/status-noreg.txt

@@ -0,0 +1,6 @@
++-----------+----------------------+
+|  STATUS   |         NAME         |
++-----------+----------------------+
+| ENCRYPTED | status-ENCRYPTED.txt |
+| NOTREG    | blah.txt             |
++-----------+----------------------+