structural/proxy: implement structural proxy pattern (#27)

* Update gitignore added JetBrains, LiteIDE and other exclude files

* Added example of proxy realisation

* Update proxy description with simple example

* Update showcase with description, small refactore of code

* Update proxy doc

* Added comments in example proxy also added link to go play sandbox

* Small improvement of proxy example

* Update link for play golang

* Corrected mistakes, splited user validation in proxy

* Updated link to play golang and some mistakes

structural/proxy.md

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+# Proxy Pattern
+
+The [proxy pattern](https://en.wikipedia.org/wiki/Proxy_pattern) provides an object that controls access to another object, intercepting all calls.
+
+## Implementation
+
+The proxy could interface to anything: a network connection, a large object in memory, a file, or some other resource that is expensive or impossible to duplicate.
+
+Short idea of implementation:
+```go
+    // To use proxy and to object they must implement same methods
+    type IObject interface {
+        ObjDo(action string)
+    }
+
+    // Object represents real objects which proxy will delegate data
+    type Object struct {
+        action string
+    }
+
+    // ObjDo implements IObject interface and handel's all logic
+    func (obj *Object) ObjDo(action string) {
+        // Action behavior
+        fmt.Printf("I can, %s", action)
+    }
+
+    // ProxyObject represents proxy object with intercepts actions
+    type ProxyObject struct {
+        object *Object
+    }
+
+    // ObjDo are implemented IObject and intercept action before send in real Object
+    func (p *ProxyObject) ObjDo(action string) {
+        if p.object == nil {
+            p.object = new(Object)
+        }
+        if action == "Run" {
+            p.object.ObjDo(action) // Prints: I can, Run
+        }
+    }
+```
+
+## Usage
+More complex usage of proxy as example: User creates "Terminal" authorizes and PROXY send execution command to real Terminal object
+See [proxy/main.go](proxy/main.go) or [view in the Playground](https://play.golang.org/p/mnjKCMaOVE).